Three computed images, centered on the optic nerve head and comparing the visibility of features, in a 61-year-old man with normal eyes. (A) Depolarized light image, (B) parallel polarized light image, and (C) average relative reflectance image. Arrows: actual sample locations for the statistical analysis. The comparison locations for computing contrast are adjacent to the sampled regions, but positioned to avoid other obvious structures such as blood vessels. These regions are not marked with arrows, because the arrows would overlap.